This invention refers to a differential transducer for measuring the curvature variations of a surface, such as a diaphragm surface.
The variation of the curvature of a surface can be due to mechanical bending forces, and especially in the case of a diaphragm due to the differential pressure on both sides of this diaphragm. A perfect knowledge of the variations of the curvature of such a body therefore procures informations on the value of these forces or said pressure difference.
The detection of the diaphragm deformation uses in general electrical circuits in which an inductance or a capacitance element changes its impedance under the influence of the deformation of the diaphragm. These techniques however have limited accuracy and a restricted dynamic range. In order to increase this range a series of sensing devices having scaled sensitivity must be implemented.
Interferometry has been used for the measurement of mechanical elongation by measuring the elongation of an optical fibre which is firmly secured to the surface undergoing deformation. The length of the optical fibre is measured by optical interferometric setups. It seems impossible to embed fibres in a differential pressure measurement diaphragm without falsifying the elastic characteristics of the diaphragm and consequently the calibration of the transducer. The accuracy of this technique is thus rather poor.
The object of the invention is to propose a differential transducer for measuring the curvature variations of a surface with enhanced accuracy and sensitivity range.
This object is achieved by the differential transducer as defined in claim 1.
The improvements as defined in claims 2 to 5 are intended to reduce the error due to the presence of the transducer on said surface.